Wonderful….BTW, I’m eternally grateful for this application. It has enhanced my life. Thank you.
Gary
Sharpcap Polar Alignment - Returning to Home loses PA
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Chuckwagon
- Posts: 40
- Joined: Thu Oct 17, 2019 1:29 am
Re: Sharpcap Polar Alignment - Returning to Home loses PA
Hi Gary,
I see Robin has gotten you further along. When I read your first post I assumed that you had finished the PA and were checking it again by going back to home as the final step. So sorry if I confused you with my description. I always finish the PA before rotating to home or anywhere else, so it just didn't occur to me that that might be what was going on. You'd have to finish each various PA to be able to compare the results and gauge if you have an issue or just normal variances.
Since I guide my CEM40, I just do the PA once and call it good enough. The minor variances you may see between Excellent and Good are unlikely to result in significant field rotation. Even if I only centered my mount on Polaris, a PA error of around 45 arc-min, and I didn't really try to polar align, the resulting field rotation for most of my imaging setups would be around 10-12 pixels over 30 minutes. And Sharpcap always gets me a sub 1 arc-minute PA, so I don't invest a ton of effort in PA when guiding.
But if you are trying to diagnose a problem, or shooting unguided, the extra efforts may be worthwhile. (and even if it's not really all that critical, I put in the extra effort with my EC mount because Sharpcap is so fast with PA and I'm sort of persnickety at times, so I feel better doing it)
Cheers
I see Robin has gotten you further along. When I read your first post I assumed that you had finished the PA and were checking it again by going back to home as the final step. So sorry if I confused you with my description. I always finish the PA before rotating to home or anywhere else, so it just didn't occur to me that that might be what was going on. You'd have to finish each various PA to be able to compare the results and gauge if you have an issue or just normal variances.
Since I guide my CEM40, I just do the PA once and call it good enough. The minor variances you may see between Excellent and Good are unlikely to result in significant field rotation. Even if I only centered my mount on Polaris, a PA error of around 45 arc-min, and I didn't really try to polar align, the resulting field rotation for most of my imaging setups would be around 10-12 pixels over 30 minutes. And Sharpcap always gets me a sub 1 arc-minute PA, so I don't invest a ton of effort in PA when guiding.
But if you are trying to diagnose a problem, or shooting unguided, the extra efforts may be worthwhile. (and even if it's not really all that critical, I put in the extra effort with my EC mount because Sharpcap is so fast with PA and I'm sort of persnickety at times, so I feel better doing it)
Cheers
Re: Sharpcap Polar Alignment - Returning to Home loses PA
Hi Chuck,
No worries, your post really woke me up to the idea of doing the PA in different ways as Robin acknowledged in his last comment. In addition to the drop from ‘excellent’ to ‘good’, that night, I was experiencing some particularly large spikes in PHD2 and was speculating whether the PA downgrade I see every time I go back up to ‘home’, was the cause in part.
I’m trying to improve all aspects of my PA and Guiding to achieve a suitable platform for imaging exoplanet transits. Before uploading transit data to global research databases, I want to do everything I can to my system to ensure quality data. This means keeping the exoplanet’s host star image on as small a group of pixels as possible - preferably just 1. To do that I’ll need to upgrade my mount and OTA, and get my PA and guiding act together and optimized. Tonight’s looking pretty clear so I’ll be trying your ideas on multi-PA positions and recording the PA results to see what works best. Thank you for helping me out.
Cheers,
Gary
No worries, your post really woke me up to the idea of doing the PA in different ways as Robin acknowledged in his last comment. In addition to the drop from ‘excellent’ to ‘good’, that night, I was experiencing some particularly large spikes in PHD2 and was speculating whether the PA downgrade I see every time I go back up to ‘home’, was the cause in part.
I’m trying to improve all aspects of my PA and Guiding to achieve a suitable platform for imaging exoplanet transits. Before uploading transit data to global research databases, I want to do everything I can to my system to ensure quality data. This means keeping the exoplanet’s host star image on as small a group of pixels as possible - preferably just 1. To do that I’ll need to upgrade my mount and OTA, and get my PA and guiding act together and optimized. Tonight’s looking pretty clear so I’ll be trying your ideas on multi-PA positions and recording the PA results to see what works best. Thank you for helping me out.
Cheers,
Gary